SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
Packet Length
Specifies the number of bytes in the entire packet. Offset bytes are not included. The sum of the Buffer_Length fields should equal the Packet_Length. Valid only on SOP. The packet length must be greater than zero. The packet data will be truncated to the packet length if the packet length is shorter than the sum of the packet buffer descriptor buffer lengths. A host error occurs if the packet length is greater than the sum of the packet buffer descriptor buffer lengths.
Start of Packet (SOP) Flag
When set, this flag indicates that the descriptor points to a packet buffer that is the start of a new packet. In the case of a single fragment packet, both the SOP and end of packet (EOP) flags are set. Otherwise,,the descriptor pointing to the last packet buffer for the packet sets the EOP flag. This bit is set by the software application and is not altered by the EMAC.
0 - Not start of packet buffer.
1 - Start of packet buffer.
End of Packet (EOP) Flag
When set, this flag indicates that the descriptor points to a packet buffer that is last for a given packet. In the case of a single fragment packet, both the start of packet (SOP) and EOP flags are set. Otherwise, the descriptor pointing to the last packet buffer for the packet sets the EOP flag. This bit is set by the software application and is not altered by the EMAC.
0 - Not end of packet buffer.
1 - End of packet buffer.
Ownership (OWNER) Flag
When set this flag indicates that all the descriptors for the given packet (from SOP to EOP) are currently owned by the EMAC. This flag is set by the software application on the SOP packet descriptor before adding the descriptor to the transmit descriptor queue. For a single fragment packet, the SOP, EOP, and OWNER flags are all set. The OWNER flag is cleared by the EMAC once it is finished with all the descriptors for the given packet. Note that this flag is valid on SOP descriptors only.
0 - The packet is owned by the host
1 - The packet is owned by the port
End of Queue (EOQ) Flag
When set, this flag indicates that the descriptor in question was the last descriptor in the transmit queue for a given transmit channel, and that the transmitter has halted. This flag is initially cleared by the software application prior to adding the descriptor to the transmit queue. This bit is set by the EMAC when the EMAC identifies that a descriptor is the last for a given packet (the EOP flag is set), and there are no more descriptors in the transmit list (next descriptor pointer is NULL).
The software application can use this bit to detect when the EMAC transmitter for the corresponding channel has halted. This is useful when the application appends additional packet descriptors to a transmit queue list that is already owned by the EMAC. Note that this flag is valid on EOP descriptors only.
0 - The TX queue has more packets to transfer.
1 - The Descriptor buffer is the last buffer in the last packet in the queue.
Teardown Complete (TDOWNCMPLT) Flag
This flag is used when a transmit queue is being torn down, or aborted, instead of allowing it to be transmitted. This would happen under device driver reset or shutdown conditions. The EMAC sets this bit in the SOP descriptor of each packet as it is aborted from transmission. Note that this flag is valid on SOP descriptors only. Also note that only the first packet in an unsent list has the TDOWNCMPLT flag set. Subsequent descriptors are not processed by the EMAC.
0 - The port has not completed the teardown process.
1 - The port has completed the commanded teardown process.
Pass CRC (PASSCRC) Flag
This flag is set by the software application in the SOP packet descriptor before it adds the descriptor to the transmit queue. Setting this bit indicates to the EMAC that the 4 byte Ethernet CRC is already present in the packet data, and that the EMAC should not generate its own version of the CRC. When the CRC flag is cleared, the EMAC generates and appends the 4-byte CRC. The buffer length and packet length fields do not include the CRC bytes. When the CRC flag is set, the 4-byte CRC is supplied by the software application and is already appended to the end of the packet data. The buffer length and packet length fields include the CRC bytes, as they are part of the valid packet data. Note that this flag is valid on SOP descriptors only.
0 - The CRC is not included with the packet data and packet length.
1 - The CRC is included with the packet data and packet length.
TO_PORT
Port number to send the directed packet to. This field is set by the host. This field is valid on SOP. Directed packets go to the directed port, but an ALE lookup is performed to determine untagged egress in VLAN_AWARE mode.
1 - Send the packet to port 1 if TO_PORT_EN is asserted.
2 - Send the packet to port 2 if TO_PORT_EN is asserted.
TO_PORT_ENABLE
Indicates when set that the packet is a directed packet to be sent to the TO_PORT field port number. This field is set by the host. The packet is sent to one port only (index not mask). This bit is valid on SOP.
0 - not a directed packet
1 - directed packet